In a radio system, interfering signals are often summed to a transmitted signal on the radio path, which makes the reception of the transmitted signal difficult. One way to eliminate signal interference in a receiver is so-called blind interference suppression, in which interference suppression is performed on the signal without knowledge of an interfering signal. In a receiver, the blind interference suppression is performed immediately after an analogue-to-digital conversion, prior to synchronization and detection of the received signal. Thus, the decision making is only based on the time and frequency information included in the received signal.
Average and median methods of frequency and time domains, for instance, represent the prior art in the receiver. In the average method, a power average is formed for signal samples, and using a preset, standardized threshold value the signal sample values exceeding the threshold value are set to zero. In the median method, in turn, from among signal samples, the samples exceeding the threshold value are zeroed on the basis of the median.
The prior art solutions have considerable drawbacks. The average method does not satisfactorily consider changes in the channel, and consequently the interference suppression remains unsatisfactory. Significant problems are encountered, for instance, in a situation, where there are few interference spikes in the received signal. The interference suppression based on the average method may then zero also samples that belong to the actual, desired signal. The median method, in which the samples have to be arranged in the order of magnitude on the basis of the value, is in turn unnecessarily complex computationally to implement in the receiver.